Seems that only Fred and one other fellow have the technical know-how to fill the slot. But after spending 24 hours in an isolation chamber adjacent to incessantly mugging, blathering, inanely role-playing Fred, the competitor is reduced to a drooling veg-head, along with everyone in the theater.

Fred certainly is a fool, observes former astronaut and control-central supervisor Bud Nesbitt (embarrassed-looking Beau Bridges). But he's also a genius when it comes to plotting landing-craft trajectories, scoping weather patterns on the Red Planet _ and emitting noxious bodily gases. Chronic indigestion apparently is not a hindrance during an eight-month space odyssey.

Joining a team that includes surly veteran ``Wild Bill'' Overbeck (William Sadler), lovely and efficient Julie Ford (Jessica Lundy), and a gregarious chimp named Ulysses, dorky, destructive Fred reveals he's not only obnoxious, but unfunny to boot. Save for a yuk or two involving (again) unspeakable odors passed from Fred's space suit into Wild Bill's, kids will be twitching in their seats over Williams' low-brow antics. Parents may want to storm the gates of Disney World and demand a refund from Michael Eisner himself.

While the others slumber in stasis during the long excursion, Fred frolics, exhibiting a banal cavalcade of bizarre voices and much imbecilic pantomime. Aghast viewers may opt for a trip to the lobby to hit skulls against the sharp corner of the concession stand. It would be more fun.

Surviving several emergencies en route is nothing compared to what's in store for the hapless crew on the surface of Mars, as dust storms threaten to scrap the mission and endanger lives. Fred's numerous bunglings amid rocks and craters always are punctuated by the disclaimer: ``It wasn't ME!''

Williams' gawky twerp also makes other odd exclamations: ``Great Alaskan asparagus tips!'' and ``Fun is my Chinese neighbor's middle name!'' Brother. This character may be the biggest idiot on two planets. Where are Varney and Shore when we really need them?